Method of producing colored flatware



Patented Sept. 26, 1939 Edward Schramm, Syracuse, N. Y., assignor toOnondaga Pottery Company, Syracuse, N. Y.,' a corporation of New York NoDrawing. Application December 30, 1938,

Serial No. 248,579

'5 Claims. (01. 25-156) The general object of the present invention isto provide an improved-method of producing American vitreous china warepieces, with their entire surfaces or large portions thereof orna- 5mentally colored. The invention is of especial utility and value whenused in the prduction of ornamentally colored American vitreous china'plates, saucers and other flat ware pieces.

The ceramic tableware identified and desig- 0 'nated herein, and notinfrequently in the art, by

the term American vitreous china,- is a commercially important type oftableware, produced in large quantities in this country by manufacturingmethods which have become standardized to the extent that theycomprisethe following steps; namely, the shaping of each ware piece from plasticmaterial of suitable composition, followed by drying, biscuit firing,glaze coating and glaze firing steps carried out in the order named. Inlieu of shaping the pieces out of material in a plastic condition, thepieces may be formed by casting in water absorbing molds, into which thematerial and water mixture is poure'd -while in a fiuid condition.Usually the ware pieces, after their biscuit firing, and prior to beingcoated with glaze forming material, are sub- Jected to an abrasive,cleaning and surface smoothing treatment, and much of such ware issubjected to underglaze or overglaze decorative treatments.

The material from which American vitreous china is made, is one oranother of various mixtures of clay, flint and fluxes such as feldspar,and calciumcarbonate in the form of whiting, the material when fused,slntering together to produce a vitreous non-absorbing body. The fusingand sintering occurs in the biscuit firing operation, which isordinarily conducted-at a temperature of about 2250" F. In the su fiquentglaze firing operation, the ware pieces are heated to a temperatureof about 2050 F. In its application to American vitreous china, the termvitreous" denotes a biscuit fired body condition of virtualnon-absorptiveness throughout the body mass, which has such resistanceto water absorption that the amount of water which the body can absorbis usually less than .5% of the dry weight of the body. Such vitreousbody condition is due to and requires a 'body of suitable compositionand its subjection to suitable processing and biscuit firing operations.

To prevent flatware pieces, such as plates and saucers, from sagging anddistortion as they soften in the biscuit flring operation, theindividual pieces are bedded or supported by pulverant non-fusiblematerial, such ,as sand or clay. Ordinarily plates and saucers areassembled in stacks for the biscuit firing operation, and .the beddingoperation involves the placing of the non-fusible bedding materialbetween each two adjacent pieces in the stack. The capacity of the warepieces to be thus bedded and supported during the biscuit firingoperation without adhering to the refractory bedding' material, is adesirable characteristic, and contributes to the satisfactory andrelatively inexpensive production of American vitreous china.

A specific object of the present invention, is to provides. method ofproducing colored chinaware of the type specified, in which the color,characteristic of the invention, is applied as an engobe to the surfacesof the ware pieces after'the latter have been shaped and dried, butprior to the ini-' tial or "biscuit" firing of the pieces, and in suchmanner as to permit the pieces to be bedded in stacks for biscuitfiring, and'to be treated in the subsequent stages of the production ofthe finished 'ware, in accordance with the standard methods heretoforedeveloped and used in the manufacture of vitreous china not so colored.

The colored engobe used in the practice of the present inventiorl,ordinarily comprises a base and color mixture, preferably applied inwater color form, consisting of from 10% to 20% of color material in theform of a metallic pigment or pigment mixture and from to of a basematerial which is of such nature, in com bination with the addedpigment, as to produce in the biscuit firing a vitreous layer,compatible in chemical and physical characteristics with the ware bodyto which it is applied and inseparably integrated therewith by fusion inthe biscuit firing. It is understood that the proportions abovementioned are merely indicative and that, in obtaining the specifiedresults, the practice of my invention is not limited to saidproportions.

A further specific object of the invention, is to provide a method ofmanufacturing American vitreous china, in which the ornamental, surfacecoloring, material applied to the surfaces of the ware pieces prior totheir first or biscuit firing,

' is of such character, and is applied in such manner, that the biscuitfiring operation makes the colored coating portion of each ware piecevitreousin the same sense in which the body of the piece is vitreous.The physical structure of a ware piece colored in accordance with thepresent inventionis thus not significantly different from that of asimilarly shaped ware piece which has undergone biscuit firing in theprocess of manufacture of vitreous china 'in the manner heretoforecustomary, and without the surface coloring characteristic of thepresent invention. Moreover, in consequence of the essential similarityin character of the colored slip and body materials, flatware pieces towhich the colored slip has been applied may be bedded in stacks forbiscuit firing in the manner customary in the production of uncoloredAmerican vitreous china, and soften, like the latter, during the biscuitfiring operation, without attaining a glassy or sticky conditionresulting in objectionable adherence of the bedding material to theware.

Since ware colored in accordance with the present invention does notdiffer significantly in physical structure or character from uncoloredAmerican vitreous chinaware, ware pieces colored in accordance with thepresent invention may be treated like uncolored American vitreouschinaware pieces, not only in the biscuit firing operation, but in allmanufacturing operations subsequent thereto. Thus biscuit fired wareproduced in accordance with the present invention has such hardness andstrength that it may be, and in a preferred practical form of thepresent invention is, cleaned and polished by a tumbling operation,carried out in a tumbling barrel or rotating container substantiallyfilled with ware pieces and abrasive material of a granular nature. Moreover, ware pieces colored in accordance with the present invention maybe subjected to any of the usual underglaze decorative treatmentsemployed in the manufacture of uncolored American vitreous china. Thevitreous condition of its colored coating portions facilitates thedecorative treatment of the ware subsequent to its biscuit firing andprior to its glaze application, particularly when that treatmentcomprises the application of decalcomania. The vitreous condition of thecolored coating portions of the biscuit fired ware also facilitates theproduction of ware having a glaze coating of fine quality.

The present invention possesses practically important advantages overthe prior methods known to me, of producing American vitreous china warepieces with their surfaces, or substantial portions thereof,ornamentally colored. The more usual prior methods involve the formationof the ware from colored bat or-body material, the underglazeapplication of the color to biscuit fired ware, and the overglazeapplication of the color to glaze fired ware. With a ware piece formedentirely from a' colored bat, it is not possible to obtain a suitablystrong color in vitreous china-ware, without high expense because of thelarge amount of relatively expensive coloring material required. Ifcolored and uncolored bats are pressed together to form a laminated warepiece, less color material is required than when the color isdistributed throughout the entire body of the piece, but color cost isstill greater than with the present invention, and the laminatedarticles are difficult to make.

The surface of vitreous china ware can be covered, in whole, or in part,by a color layer applied on the biscuit fired ware prior to the glazing.However, with that process, it is difficult, if the area colored belarge, to secure uniformity of color. Furthermore, it ,is practicallyimpossible to impose ordinary underglaze decorative treatments on thesurface portions of the biscuit fired ware to which the color layerhasbeen applied, unless after the color layer application, the ware issubjected to a special firing operation, preceding the regular glazefiring operation. As previously explained, ordinary underglazedecorative treatments can be applied to biscuit fired ware to whichcolor has been applied in accordance with the present invention, withsubstantially the same freedom and ease as they can be applied touncolored biscuit fired ware.

The overglaze application of the coloring agent involves a third firingof the were in a decorating kiln at a temperature of about 1350 F., andnecessarily results in a relatively high cost of production.Furthermore, the overglaze color application, like the usual overglazedecorative effects, rubs of! or wears away in time.

Color applied to ware in accordance with the present invention does notwear or rub of! because it is protected by the glaze, which is notaffected by the color, and like the glaze coatin of ordinary uncoloredAmerican vitreous china, is transparent, strong and wear-resistant.

Color effects have also been obtained by using colored glazes, but thismethod has distinct limitations, especially as applied to Americanvitreous china, due chiefly to the difficulty of applying thecoloredgla'ze with uniformity on a virtually non-absorbent body, and tothe fact that the coloring matter in the glaze may adversely affectproperties of the finished glaze, and to the further fact that coloredglazes necessarily tend to mask underglaze decorative treatment effects.

In another known method of obtaining colored ware, first a coloredengobe and then a coating of transparent colorless glaze formingmaterials, are applied to the dried but unfired ware, after which thelatter is subjected to one fire operation simultaneously affecting thebody, engobe, and glaze. The use of this method is limited by thedifficulty often involved in the application to the unfired ware of thetwo coatings-the engobe and the glaze-and the method is not usable inthe production of fiat ware pieces which must be em-- bedded inrefractory material for the biscuit firing operation, as the bedding orsupporting material would adhere to the glaze surface. Anotherdisadvantage of the last mentioned method, is that desirable decorativetreatments such as commonly are used in the chinaware industry, cannotbe readily applied to ware so treated prior to its firing.

A very important feature of the present invention is the practicalapplication of one decorative color treatment superimposed on anotherdecorative color treatment, at reasonable cost. Heretofore this has beenpractical as applied to the manufacture of American vitreous chinaware,

only by the use of methods involving either pigmented bodies, overglazedecorations, or base layers of color applied on the biscuit fired ware,which layers must be given an additionalfiring to fuse the color, beforeapplying another color treatment thereon. The objections to the firsttwo methods mentioned, have been made clear above. The objection to thelast mentioned method is, of course, the added expense of the additionalfiring which it requires. The present invention makes practical, and atreasonable expense, an unlimited number of desirable combinations ofcolored decorative treatments, one superimposed on the other, and allapplied underglaze, thereby being protected by the glaze from wearingof! in service.

A preferred and inexpensive method of carryis to use a guard .ofsuitable material and contour to cover that portion of the ware piecewhich is to be left in the natural body color, and then to apply thecolored engobe to the balance of the piece by spraying the engobethereon by an fair b I The invention has certain practicallydesirablecharacteristics not. previouslyv mentioned. For one thing, it permitsproper protection of delicate colors. In the usual method of applyingunderglaze color to biscuit fired wares, certain colors, notably,delicate pinks, yellows and light greens, are of such nature that thereis a tendency to their destruction by the action of the glaze in theglost firing operation, and a tendency for such 'colors to come from theglost firing kiln with nonuniform color values. With the presentinvention, delicate colors can be immutably fixed in the biscuit firingoperation, so as not to be subject to alteration in the subsequent glostfiring.

The invention permits of new color combinations in that it is readilypractical to combine the use of an engobe of any desired color' appliedin accordance with the present invention with the use of certain regularunderglaze colors which require the subsequently applied glaze materialsto be of a special character suitable for the protection and developmentof the particular underglaze colors employed, and not suitable forcertain other such colors, since, in general, the engobe color is notadversely affected by the use of the special glaze materials required toprotect sible with the invention to obtain brilliant reddish browns, inconjunction with delicate pink and green underglaze decorative effects.

' Q Having now described my invention, what I claim as new and Patent,isz' 1. The method of producing surface colored American. vitreous chinawarewhich consists in shaping said ware froin'body, material in a moistcondition and of such composition as to be fused and sintered by abiscuit firing operation into a hard vitreous body characteristic ofAmerican vitreous chinaware, drying the shaped ware and thereaftercoatingthe ware surface to be colored with an engobe comprising apigmented material, biscuit firing the coated ware, said pigmentedmaterial being of such composition that it is fused and sintered by thebiscuit firing operation into a colored surface portion of the ware inpermanent adherence, and similar inhardness and in its vitreouscharacter, to said fused and sintered body, coating the biscuit firedware with glaze forming material, and then'glaze firing desire to secureby Letters and develop the said regular. underglaze decorative'colorapplications. For example, it is pos-,

a surface.

the ware at a temperature below the biscuit firing temperature.

2. The method of producing surface colored American vitreous china warewhich consists in shaping said ware from body, material in a moistcondition and of such composition as to befused and sintered by abiscuit firing operation into a hard vitreous body characteristic ofAmerican vitreous chinaware, drying the shaped ware and thereaftercoating the ware surface to be colored with an engobe comprising apigmented material,

biscuit firing the coated ware, said pigmented material being of suchcomposition that it is fused and sintered by the biscuit firingoperation into a colored surface portion of the ware in permanentadherence, and similar in hardness and in its vitreous character, tosaid fused and'sintered body, applying, a decorative design to theengobe treated surface of the biscuit fired ware, then coating the warewith glaze forming material and then glaze firing the ware at atemperature below the biscuit firing temperature.

3. The method of producing surface colored American vitreous chinaflatware pieces, which consists inshaping said pieces from body materialin a moist condition and of such composition as to be fused and sinteredby a biscuit firing operation into a hard vitreous body character-'istic of American vitreous chinaware, dryingv said pieces and thereaftercoating the surfaces to be colored with anengobe comprising a pigmentedmaterial, and further drying-the ware pieces, bedding the ware pieces instacks with pulverant non-fusible material interposed between adjacentpieces in the stack, biscuit firing the bedded stacks,said engobe beingof such composition that it is fused and sintered by the biscuit firingoperation into ,a colored surface portion of the ware integrallyconnected with,

and similar in hardness and in its vitreous character to said fused andsintered body, without gobe covered portions of the surfaces of thebiscuit fired ware pieces prior to coating said pieces with glazeforming material.

5. The method specified in claim 1, in which, prior to being coated withthe glaze forming material, the biscuit fired ware pieces are cleanedand polished by. a tumbling action and decorative designs aresuperimposed on the engobe covered portion of the cleanedand polishedware

